The law of multiple proportions is one of the fundamental laws of stoichiometry and was first discovered by the English chemist John Dalton in 1803. The law states that when chemical elements combine, they do so in a ratio of small whole numbers. For example, carbon and oxygen react to form carbon monoxide (CO) or carbon dioxide (CO2), but not CO1.3. Further, it states that if two elements form more than one compound between them, the ratios of the masses of the second element to a mass of the first element will also be in small whole numbers. (wikipedia)